Deformable die apparatus for tube drawing

ABSTRACT

VARIABLE DIE APPARATUS FOR TUBE DRAWING WHEREIN A DIE RING OF DEFORMABLE MATERIAL, PREFERABLY A STRONG ELASTOMER, IS CIRCUMFERENTIALLY CONFINED AND IS CAUSED TO BE DEFORMED BY FORCE-APPLYING MEANS SO THAT ITS INNER DIAMETER VARIES, SAID FORCE-APPLYING MEANS PREFERABLY BEING HYDRAULICALLY ACTUATED AND OPERATING UPON THE DEFORMABLE DIE RING EXTERNALLY IN ONE FORM OF THE INVENTION AND INTERNALLY IN ANOTHER FORM OF THE INVENTION.

Feb. 23, 1971 w H|N$HAw 3,564,884

DEFORMABLE DIE APPARATUS FOR TUBE DRAWING Filed Aug. 20, 1968 2Sheets-Sheet 1 fvvs/vrae f JIM/v W II/Mswnw s WM 07 roe/vs Vs.

Feb. 23, 1971 J. w. HINSHAW DEFORMABLE DIE APPARATUS FOR TUBE DRAWINGFiled Aug. 20, 1968 2 Sheets-Sheet 2 IN YEN 70A? Jb/wv I4 Ll/NsunwIOTTOENEr J- United States Patent 3,564,884 DEFORMABLE DIE APPARATUS FORTUBE DRAWING John W. Hinshaw, Garden Grove, Califi, assignor to BattelleDevelopment Corporation, Columbus, Ohio, a corporation of Delaware FiledAug. 20, 1968, Ser. No. 753,907 Int. Cl. B21c 3/06 US. Cl 72--57 6Claims ABSTRACT OF THE DISCLOSURE Variable die apparatus for tubedrawing wherein a die ring of deformable material, preferably a strongelastomer, is circumferentially confined and is caused to be deformed byforce-applying means so that its inner diameter varies, saidforce-applying means preferably being hydraulically actuated andoperating upon the deformable die ring externally in one form of theinvention and internally in another form of the invention.

BACKGROUND OF THE INVENTION In some types of tube drawing operations, asfor example in the drawing of cylindrical tubing into a taperedconfiguration, it is necessary to employ a drawing die which is variablein ID. According to typical prior art practice such a variable drawingdie will be composed of a solid metal ring which is sufficiently ductileto allow the ring to expand as it draws the tube down against a taperedmandrel from the small diameter end of the mandrel up to the largediameter end thereof.

A major problem in the use of this and other variable die devicesemployed in the prior art for tube drawing was that the operator hadvery little control over the changes in the die shape and size, or inthe amount of radially inwardly directed confining force which the diehad on the workpiece. A related problem in connection with the use ofsuch prior art variable tube drawing dies was that in general they wouldonly function satisfactorily over a relatively small variation in size.

A still further problem in connection with conventional variable diesfor tube drawing is that while such dies could sometimes be made fairlyreliable for tube drawing operations wherein the die would expand, asfor example when drawing up a taper, they nevertheless were generallyineffective or unreliable where attempts were made to constrict themduring a drawing operation, as for example when drawing down a taper.

SUMMARY OF THE INVENTION In view of these and other problems in the art,it is an object of the present invention to provide variable dieapparatus for tube drawing which employs as the means operating upon thetube a die ring composed of a material such as an elastomer which isdeformable over a much greater range of sizes and shapes than aconventional metal drawing die ring, the apparatus including selectivelyoperable means for deforming the die ring radially inwardly or relaxingthe die ring from such deformed condi tion, whereby tubing can be drawnwith large variations in its diameter and cross-sectional configuration.

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Another object of the invention is to provide variable die apparatus ofthe character described for tube drawing wherein the deformable die ringemployed therein is composed of a strong material which has good elasticproperties, whereby the deformable die ring will elastica ly return tosubstantially its initial undistorted condition after completion of atube drawing operation therewith, permitting the deformable die ring tobe reused for a number of different tube drawing operations.

A further object of the invention is to provide variable die apparatusof the character described for tube drawing wherein the deformable diering which operates upon the tube is circumferentially confined and iscaused to be deformed for variation of its ID by hydraulically actuatedmeans which affords the operator wide latitude in controlling the ID ofthe deformable die ring and in the amount of constricting force of thedeformable die ring against the tube that is being drawn.

A still further object of the invention is to provide variable dieapparatus of the character described wherein the die ring of deformablematerial is circumferentially confined and is varied in ID by axialcompression of the ring between opposed surfaces on members which areadjustable relative to each other in the axial direction, preferably byhydraulically actuated means.

Another object is to provide variable die apparatus of the characterdescribed wherein the deformable die ring which operates directly uponthe tubing that is being drawn is hydraulically actuated for variationof the ID thereof and the amount of force applied by the ring againstthe tubing by application of hydraulic pressure to the inside of thedeformable die ring and release of such pressure therefrom.

An additional object of the invention is to provide variable dieapparatus of the character described for tube drawing wherein the diering is composed principally of a deformable material such as a strong eastomer, but also includes an expansible spring metal core which tendsto retain the initial cross-sectional shape of the die ring as the diering contracts or expands circumferentially and hence radially.

Further objects and advantages of the present invention will appearduring the course of the following part of this specification, whereinthe details of construction and mode of operation of several preferredembodiments are described with reference to the accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an axial sectionillustrating assembled deformable die apparatus according to theinvention with the parts thereof in their unactuated condition and thedeformable die ring in its relaxed condition.

FIG. 2 is a fragmentary axial section similar to FIG. 1, butillustrating the apparatus in an actuated condition, with the deformabledie ring deformed and squeezed inwardly, the apparatus having beenemployed to draw down a taper.

FIG. 3 is a cross-sectional view taken on the line 33 in FIG. 2.

FIG. 4 is a side elevational view, partly in axial section, of thedeformable die ring of FIGS. 1 and 2 separated from the remainder of theapparatus and in its relaxed condition.

FIG. is a side elevational view, partly in axial section, similar toFIG. 4, but illustrating a second form of deformable die ring whichincludes an expansible, split spring metal ring molded therein toincrease the crosssectional rigidity of the deformable die ring.

FIG. 6 is an axial sectional view similar to FIG. 2, but illustratingthe apparatus after it has been employed to draw back up a taper on thesame tube, the apparatus still being slightly actuated :but approachingreturn to its condition of repose.

FIG. 7 is an axial section, partly in elevation, illustrating variabledie apparatus similar to that shown in FIGS. 1 to 6, but wherein thedeformable die ring is of generally hexagonal shape, and is in theprocess of applying a taper of hexagonal cross-section to an initialcylindrical tube.

FIG. 8 is a cross-sectional view taken on the line 8-8 in FIG. 7.

FIG. 9 is a perspective view of the piston portion of the apparatusshown in FIGS. 7 and 8, with the hexagonal die ring of deformablematerial shown in phantom in axially exploded relationship relative tothe piston.

FIG. 10 is an axial sectional view showing still another form of diering according to the invention disposed in its die holder seat, thisform of ring defining a hollow annulus therein for receiving hydraulicfluid under pressure to cause radial deformation thereof.

DETAILED DESCRIPTION Referring at first to FIGS. 1 to 4 of the drawings,the deformable die apparatus which is illustrated in these figuresemploys a die ring 10 composed of a plastic material which isresiliently deformable. The hardness of the deformable die material willvary according to the strength and thickness of the wall of the tubingthat is being drawn, and according to the configuration to which thetubing is being drawn. However, where the apparatus is to be employedfor drawing most types of metal tubing, it is preferred that thedeformable die ring 10 be composed of an elastomer material which hasthe characteristics of being generally rigid and tough, but deformableor distortable upon the application of substantial unbalanced forcesthereto. A material which has been found particularly suitable for useas a deformable die ring in drawing tapered copper and aluminum tubes isElastacast polyurethane produced b Acushnet Process Company. It is to beunderstood, however, that the present invention is not limited to theuse of any particular resilient deformable material for the deformabledie ring 10, and that a variety of different materials will be suitablefor different tube drawing applications.

The deformable die ring 10 includes generally flat, parallel sidesurfaces 12', a generally cylindrical annular outer surface 14, and aninner annular surface 16 which is rounded in cross-section.

The deformable die ring 10 is supported in a die holder sleeve 18 havingan annular body portion 20, a generally flat or radially orientedannular shoulder 22 against which one of the side surfaces 12 of diering 10 seats, and a generally cylindrical skirt portion 24 which ispreferably slightly greater in axial dimension from the shoulder 22 thanthe thickness of the die ring 10 between its side surfaces 12. Thus, thedeformable die ring 10 in its relaxed condition as shown in FIGS. 4 and1 fits entirely within the cylindrical skirt portion 24 of the dieholder sleeve 18, being slightly recessed inwardly from the outer end ofthe skirt 24, and seating flush against the shoulder portion 22 of dieholder sleeve 18.

The die holder sleeve 18 is mounted inside a 'hydraulic cylindergenerally designated 26, and including a cylindrical barrel 28 withinwhich the sleeve 18 is fitted. The cylinder 26 has an end plate 30 onone end thereof against which the body portion of the die holder sleeve18 4 abuts, the end plate including a cylindrical flange threadedlyconnecting the end plate 30 to the barrel 28. The end plate 30 has acentral aperture 34 therethrough which is axially aligned with, andsubstantially the same size as, the passage through the body portion 20of die holder sleeve 18.

The cylinder'barrel 28 is provided with an in-turned end flange 36 atits other end, the flange 36 defining a circular aperature 38 that issomewhat larger in diameter than the aperture 34 in end plate 30.

A piston 40 is slidably engageable within the cylinder barrel 28, and isintegrally formed on the inner end of a hollow piston rod 42 whichextends out through the aperture 38 defined by the cylinder end flange36. A pair of T sealing rings 44 on the piston provide a fluid-tightseal between the piston and cylinder barrel, and the fluid-tight sealwithin the cylinder between the piston and cylinder end flange 36 iscompleted by a further sealing ring 46 in the cylinder end flangeaperture 38.

Hydraulic fluid is introducible through fluid line 48 from a suitablefluid pressure source (not shown) and through port 50 into the annularcylinder chamber 52 behind piston 40 to drive the piston to the right asillustrated in FIGS. 1 and 2. The piston includes an annular pressureface 54 which is engageable against the exposed side surface 12 of thedeformable die ring 10 as the piston is forced to the right in FIGS. 1and 2, to compress the die ring 10 in the axial direction and therebyforce the rounded inner die surface 16 to constrict from its position ofrepose as illustrated in FIG. 1 to a substantially constricted positionas illustrated in FIG. 2. It will be noted that the annular pressureface 54 on the piston is slightly frusto-conical in configuration. Thisangle on the pressure face 54 causes the inner peripheral edge of theface 54 to first contact the deformable die ring 10 adjacent the roundedinner working surface 16 of the die ring. Then, as the inclined pressureface 54 compresses the deformable die ring 10 it tends to lock the diering material in its operative position and to direct the displaced ringmaterial substantailly entirely radially inwardly as best illustrated inFIG. 2.

It will be apparent that the greater the hydraulic pressure applied inthe cylinder chamber 52, the tighter the piston will axially squeeze thedeformable die ring 10, and the greater the radially inwardly directeddeformation of the die ring 10 will be. Conversely, by allowing thehydraulic pressure to bleed out of cylinder chamber 52 through port 50and conduit 48, the resiliency of the deformable die ring 10 will causethe die ring to resume its original, relaxed shape as illustrated inFIGS. 1 and 4, the die ring moving the piston 40 back to the left as itthus resumes its initial configuration. Accordingly, the fluid pressuresource connected to fluid conduit 48 is adapted to supply fluid over aWide range of pressures 'as required for any particular formingoperation, and is also provided with bleeder valve means to allowselective reduction of the pressure from the cylinder when desired.

The piston is provided with an annular recess immediately radiallyoutwardly of the pressure face 54 thereon to accommodate the outer edgeportion of the die holder skirt 24 as best shown in FIG. 2. By thismeans, the outer peripheral edge of the deformable die ring 10 issubstantially completely circumferentially confined during the time thatthe piston 40 is applying axial compression to the die ring 10.

FIG. 2 illustrates a tube drawing operation wherein an initiallycylindrical tube 58 is supported at one end by an end plug 60 andclamped at that end between jaws 62 to secure that end of the tubeagainst axial movement, and the tube 58 is then moved axially to theright while hydraulic fluid pressure is increased in the cylinderchamber 52 so that the piston gradually squeezes the deformable die ring10 radially inwardly to apply a taper 64 to the tube 58. Drawing downthe taper as illustrated in FIG. 2 can be accomplished by the presentinvention without requiring that the taper be drawn over a taperedmandrel. Drawing down a taper is very difficult to accomplish withconventional variable drawing dies, while it is relatively easy toaccomplish with the present invention.

FIG. illustrates a second form of deformable die ring a which is thesame as die ring 10 except for the inclusion within the resilientplastic material of an expansible, split spring metal ring 66 having agenerally circular overall cross-sectional shape. This metal ring 66assists the deformable die ring 10a to retain the desired curvature ofits rounded inner working surface 16a as the die ring is beingcompressed axially and thereby deformed radially inwardly.

FIG. 6 shows the deformable die apparatus of FIGS. 1 to 4 with the tube58 drawn further therethrough in such a way as to draw back a taperafter reaching a point 68 along the tube 58 of desired minimum diameter.As the portion 64 of the tube was being drawn through the deformable diering 10, increasing pressure was supplied to the cylinder chamber 52 toprogressively constrict the deformable die ring 10 about the tube so asto progressively constrict the tube 58 down to the point 68 of minimumdiameter. Then, as tube 58 continued to be drawn to the right throughthe deformable die ring 10 as illustrated in FIGS. 2 and 6, thehydraulic pressure in cylinder chamber 52 was gradually reduced to allowgradual enlargement of the inner working surface 16 of the deformabledie ring and consequent gradual enlargement of the tube 58, so as toproduce the reverse tapered portion 72 of the tube 58. This reversetapered portion 72 is almost completed in FIG. 2, and the net result isthat the tube 58 has been formed into the shape of a venturi tube,

With the present invention tubes may be drawn either down or up a taper,or may be drawn into abruptly or gradually stepped configurations ofdifferent diameters, or may be otherwise shaped without requiring theuse of mandrels within the tube. However, if desired, a mandrel may beemployed to assure the operator of an accurate formed tubeconfiguration, or to simplify the control required by the operator. Forillustrative purposes a tapered mandrel 74 has been shown in the reversetapered portion 72 of tube 58 in FIG. 6.

FIGS. 7 to 9 illustrate an alternative form of the invention which isadapted to draw tubing into a cross- Sectional shape other than round,in this case a hexagonal shape. In this form of the invention the diering 10b is hexagonal both in OD and ID, as best shown in solid lines inFIG. 8 and in phantom in FIG. 9. Otherwise, the die ring 10b is the sameas die ring 10 of FIGS. 1 to 4 and 6. Although the ID of the die ringmay be provided in an cut-of-round shape while leaving the OD round, itis preferred to provide the OD in substantially the same outof-roundconfiguration as the ID to prevent distortion of the ID as the die ringis squeezed axially and the OD correspondingly contracted to a smallersize.

The apparatus of FIGS. 7 to 9 employs the same cylinder 26 as theapparatus of FIGS. 1 to 3 and 6, but the die holder sleeve 18b ismodified so that the skirt portion 24b thereof has an ID complementaryto the OD of the die ring 10b, in this case hexagonal. Similarly, thepiston 40b is modified from the piston 40 of FIGS. 1 to 3 and 6 byproviding the pressure face 54b thereof with outer dimensions whichconform with those of the die ring 10b, in this case hexagonal.Accordingly, the inner axially oriented wall of recess 56b is ofhexagonal shape.

FIGS. 7 and 8 illustrate drawing an initially cylindrical tube 58b withthe apparatus of FIGS. 7 to 9 so as to produce a tapered portion 64bthereof having a hexagonal cross-section. This operation is illustratedin FIG. 7 as being performed in the same manner as the tapering with acircular form in FIG. 2, by drawing down the taper while graduallybuilding up the hydraulic pressure in cylinder chamber 52 so as toprogressively constrict the hexagonal die ring 10b.

It will be apparent from FIGS. 7 to 9 and from the foregoing descriptionof the apparatus there illustrated that the deformable die ring may beprovided in a variety of circumferential shapes to draw tubing into acorresponding variety of circumferential shapes, all within the scope ofthe present invention.

FIG. 10 illustrates another form of the invention wherein the deformabledie ring 10c is similar to the deformable die ring 10 in overallconfiguration and composition, but differs by being hollow, having atorus-shaped annular recess 76 therein which communicates through afluid conduit 78 with a variable source (not shown) of fluid pressure.The conduit 78 may extend through the body of die holder sleeve 180which is otherwise similar to the die holder sleeve 18 of FIGS. 1, 2 and6, and thence through a suitable accommodation in the cylinder endplate.

If desired, the hollow deformable die ring may be employed in the sameapparatus as the deformable die ring 10, which apparatus is shown inFIGS. 1 to 3 and 6, but will permit added operator control by the directapplication of fluid pressure within the die ring 100 or release offluid pressure therefrom. Alternatively, the hollow deformable die ring100 may be employed in die holder apparatus not otherwise adjustable, asfor example in apparatus similar to that shown in FIGS. 1 to 3 and 6 butwherein the piston pressure face 54 is fixedly positioned relative tothe die holder sleeve 18c. In such case, the entire control will beaccomplished by adjustment of the fluid pressure within the torus-shapedannular recess 76 in the die ring 100.

While it is contemplated that the deformable die ring of the presentinvention will, in many tube drawing operations, be deformed byhydraulic actuating means radially inwardly during the drawingoperation, it is to be understood that the deformable die ring of theinvention is equally applicable to use where it is initiallyconstricted, as by hydraulic actuating means, and then is graduallyrelaxed by release of the hydraulic pressure actuating means so as to beallowed to radially expand. It will be apparent from the accompanyingdrawings and the foregoing description that one of the basic advantagesof the present invention is the fact that a wide latitude of control ispermitted over the ID of the deformable die ring during operation.

While the instant invention has been shown and described herein in whatare conceived tobe the most practical and preferred embodiments, it isrecognized that departures may be made therefrom within the scope of theinvention, which is therefore not to be limited to the details disclosedherein, but is to be accorded the full scope of the appended claims.

I claim:

1. In tube drawing mechanism of the type having a drawing die throughwhich a tube is adapted to be drawn, a die holder, and drive meansengageable with the tube for applying axial movement of the tuberelative to the die holder so as to drive the tube through the die, thecombination with said mechanism of variable die apparatus whichcomprises a die ring composed of resiliently deformable material andhaving a generally radially inwardly directed working surface, supportmeans forming a part of said die holder peripherally confining said diering and partially confining the ring in the axial direction, andselectively operable means that is operable independently of said drivemeans for deforming the die ring so as to vary the size of said innerworking surface.

2. Variable die apparatus as defined in claim 1, wherein said die ringis composed of a generally rigid but elastically deformable plasticmaterial.

3. Variable die apparatus as defined in claim 1, wherein said die ringhas an expansible annular spring metal core member embodied therein.

4. Variable die apparatus as defined in claim 1, wherein said means fordeforming the die ring comprises an annular hydraulic chamber definedwithin said deformable die ring, and conduit means connected to the diering and communicating with said chamber for introducing hydraulicpressure therein.

5. Variable die apparatus as defined in claim 1, wherein said workingsurface has an out-of-round circumferential shape, and the outerperiphery of the die ring has a similar, complementary out-of-roundcircumferential shape.

6. Apparatus as defined in claim 1, wherein said radially inwardlydirected working surface of the die is inwardly convexly rounded inaxial cross section.

References Cited UNITED STATES PATENTS RICHARD J. HERBST, PrimaryExaminer U.S. Cl. X.R.

